Block them.

They have already lost my trust when they said that I have an outdated version Firefox when I visited them.

Hi,

Unfortunately we had a data base error today and lost some user accounts when we had to go back to our backups. If you have started this thread, your's is one of those. Since we can not recreate your account, please sign-up for a new account here to reply to the forum messages:

https://support.mozilla.org/users/auth

You can use the same username and email address as before. We are very sorry for the inconvenience.